Amy got to be in london. We're at the "gma" pool. A swim-up refreshment bar here. We're talking about a workout. It's like a spin class. It takes place underwater. It's called aqua cycling. You can pedal your way to finance. Bianna golodryga checked it out. Reporter: In just a few years, cycling has gone from this to this. Pulsating music. Intense instructors. And lots and lots of sweat. Now the newest fitness sensation to make a splash is aiming to take the intensity and sweat and, well, dunk it. This is aqua cycling. It's very similar to indoor cycling class. The main difference is you pedal against the water. Take the right hand. Reporter: Already popular in europe, esther is hoping aqua cycling make waves in the u.S. She just opened aqua studio in new york. The first its kind in the country. How does that differ from pedal on land? It protects your muscles, your bones. Reporter: Fins, towel, ready to spin. Let's do it. Three, two, one, down. How is everybody doing? Reporter: I am starting to sweat. Me, too. You feeling that bianna? Yeah. You can feel the buns firing up. Reporter: And it's not just your legs getting a workout. Up for two. Take it down. Reporter: And while spinning in a two piece might not be ffr everyone, the women in this class took it swimmingly. This takes it to another level. Reporter: At $40 a class, it's not cheap. I felt like I got a full-body workout. Perhaps the best part of aqua cycling, no one can tell how much you sweat. Speaking of someone taking it for the team, natalie and I are freezing in the water right now. We don't recommend throwing your old stationary bikes in the pool. These are specially made for the water. You need special shoes to protect your feet. We don't have them right now.

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